1. Field of the Invention
The present invention generally relates to communications devices, and more particularly to a radio communications device capable of varying a transmission frequency and/or a transmission power level.
2. Description of the Related Art
A radio communications device has been practically used in which operation parameters such as the transmission frequency and the transmission power level can be varied. Conventionally, switches for setting variable parameters are attached to the panels of transmitters and receivers. A controller having the setting function, such as a central processing unit (CPU), has also been employed. Use of switches for parameter setting makes it possible for the operator to see and confirm the actual setting of a desired parameter. However, spaces for providing such switches are needed on the transmitters and receivers. This prevents down-sizing. If the controller is used together with switches for setting, the same problems as described above will take place.
An improved controller cooperating with an EEPROM (Electrically Erasable and Programmable Read Only Memory) has been proposed. The desired parameter values are written into the EEPROM, and the controller reads the parameter values therefrom. Use of the EEPROM does not need switches for setting. However, the operator cannot directly confirm the parameter values stored in the EEPROM. With the above in mind, conventionally, the controller executes an initial program, which reads the parameter values from the EEPROM and displays these values on a display unit at the time of power on. The operator sees the parameter values on the display and determines whether or not the parameter values have been correctly set.
If a fault has occurred in a radio communications device, a prompt response is required. For example, a spare unit is substituted for the defective unit in the radio communications device. At this time, it is necessary to set, again, the same desired parameter values as those used before a fault occurs after the substituting operation is completed. As has been described previously, the parameter values are, for example, the transmission frequency and the transmission power level. If a large number of items should be set, an erroneous setting operation may be performed in practice. Hence, it is necessary to perform a check process in order to prevent communications from taking place with an erroneously set parameter value. This increases the load of the operator and prevents quick recovery work.
Hence, it is required that the parameter setting in a radio communications device operating on the variable parameters such as the variable transmission frequency and the transmission power level can be correctly carried out and that transmission can be automatically inhibited if an erroneous parameter is set. Particularly, when a defective unit is replaced by a new one, the parameter setting should be quickly and easily performed.
It is an object of the present invention to provide a communications device which meets the above requirements.
A more specific object of the present invention is to provide a communications device having the function of automatically detecting erroneous setting and automatically inhibiting transmission when erroneous setting is detected, and having a simplified setting operation.
The above objects of the present invention are achieved by a communications device comprising a first memory unit storing parameter information which defines an operation of the communications device, a second memory unit storing parameter information which defines the operation of the communications device, the parameter information stored in the first memory unit coinciding with that stored in the second memory means when a communication can take place, and a control unit, operatively coupled to the first memory unit and the second memory unit, for determining whether or not the parameter information stored in the first memory unit coincides with that stored in the second memory unit and allowing a transmission operation of the communications device based on the parameter information when it is determined that the parameter information stored in the first memory unit coincides with that stored in the second memory unit.